1. Technical Field of the Invention
This disclosure relates to a technology for processing digital image data in a digital multifunction product (MFP) and in an image processing apparatus.
2. Description of the Related Art
Technologies of an image reading unit using a line sensor formed with a charge-coupled device (CCD) or a photoelectric transducer and of a toner-image writing unit using laser radiation have advanced. Based on the advanced technologies and from analog copiers, digital copiers that copy images using digitized image data have appeared on the market.
The digital copier has high compatibility with other units that handle digital image data, and is combined with not only a function of a copier but also with various functions such as a facsimile function, a printer function, and a scanner function. Therefore, the digital copier is not a simple digital copier, but is called “digital multifunction product (MFP)”.
Varieties of functions are incorporated in the MFP in association with the progress in the technologies related to the MFP such as increased memory capacity of a hard disk drive (HDD), reduction in costs, speeding-up and spread of the communication technology such as networks, improved throughput of central processing unit (CPU), and technologies related to digital image data such as compression technology.
Meantime, the MFP is used in various ways. For example, a compact MFP is set next to a personal computer (PC) so that an operator can easily use the functions of a copier, a facsimile, a printer, and a scanner. A medium-scale MFP is shared by a plurality of members in a department or in a section so that the members can use functions of achieving a certain amount of productivity such as sorting, punching, and stapling. Alternatively, a large-scale, highly productive, high-quality MFP is used in a department of companies that concentratedly performs a copy-related work or used in companies that perform a copy-related service as business.
As explained above, the MFP is diversified into various types from a compact class to a large-scale class. Some of the functions of the MFP are shared by the classes, but some of the functions are strongly required in each particular class.
For example, post-processes for paper after an image is plotted thereon such as punching, stapling, and folding the paper, and electro-filing performed simultaneously with copy work are required for the large-scale MFP. On the other hand, provision of an Internet-FAX function and a PC-FAX function is required for the compact MFP, and as a personal use, high-quality image printing for special paper is also required for the compact MFP.
New and various types of functions are provided in the MFP, and it is desired to provide further new functions and a combination of a plurality of functions. Conventionally, a system is constructed so as to incorporate a set of functions required for all classes therein, and is provided to diversified MFP market.
It is recognized that the value of information is important in business, and information is therefore required to be delivered not only quickly, accurately, and reliably, but also understandably and effectively. A new function of effectively handling information using digital data is provided in association with speeding-up and spread of communication technology, increased capacity of memory, reduction in costs thereof, and downsizing thereof, and high performance of PC. Therefore, provision of a new function and a combination of the functions are desired also in the MFP that handles digital image data which is one of digital data.
The provision of a new function and the combination of functions progress in the above manner, and it thereby becomes important for a digital color MFP including various color image input/output units to minimize the increase in costs as low as possible and obtain output images with less degradation in image quality.
To solve the problems, in Japanese Patent No. 3134756, input image data and image-area separation data generated by an image-area separating unit are compressed and stored, and when it is to be output, expanded image data is subjected to image processing based on a detected image attribute and the image-area separation data.
In Japanese Patent No. 3368143, predetermined logic operation is subjected to information described in a page description language based on a type, a category, and an attribute of an image to generate a characteristic signal, and image processing is performed for each pixel according to the characteristic signal.
In Japanese Patent No. 3695498, when an image file described in a predetermined format is interpreted and expanded to image data, tag data indicating an attribute is also generated for each pixel, and the generated data is compressed and stored. And a time at which these pieces of image data are read in a time division mode is variably controlled.
The increased capacity and reduction in costs of memory are combined with the functions of the MFP. Recently, in association with the combination, the following usage of the MFP is increased. Digital image data created by reading a paper document and digital image data sent from a PC or external media are stored in the MFP, and are output again when these pieces of information are required.
When the digital image data stored in the MFP is to be output again, a certain time has often passed since the data has been stored. Therefore, situations i.e. requirements and needs of an operator who wants to re-output the data may often change during the time, and thus, the functions of the MFP cannot respond to the change of the requirements and needs. For example, when the operator wants to facsimile-transmit the digital image data which is stored in the MFP upon using the copier function, the data cannot be used in a required manner, or even if possible, the image quality may be greatly changed or productivity may decrease significantly.
There is also a case where, when the copier function is used in such a manner that two A4 documents are combined in a sheet of A4 recording medium, such image data is stored in the MFP. When the stored image data for the two A4 documents are to be plotted on two sheets of A4 recording medium, the image data cannot be output in that mode, or even if possible, the image quality may be greatly changed or productivity may drop significantly.
In both cases, it is fundamental for the digital color MFP including various color image input/output units to minimize the increase in costs as low as possible and generate output images with less degradation in image quality. However, to obtain high quality output images, it is necessary to handle supplemental information indicating features of input image data as well as the input image data, as described in Japanese Patent No. 3134756 on a paper document and in Japanese Patent No. 3368143 on an image file sent from a PC and a network.
In an actual case, it is necessary to compress and store the input image data and the image-area separation data generated by the image-area separating unit as described in Japanese Patent No. 3134756. However, to minimize degradation in image quality as low as possible, especially the image-area separation data indicating the feature of each pixel is desirably reversible. Therefore, if the entire image attribute and the image-area separation data detected by the image-area separating unit are stored, this leads to a large increase in costs.